The present invention generally relates to processing a semiconductor substrate. In particular, the present invention relates to a system and method of forming layers and structures on a wafer integrated with sensors to monitor wafer changes and thus optimize uniform layer and structure formation.
Many modem integrated circuits generally include multiple layers of metallic or conductive wiring surrounded and covered by insulating or dielectric layers. Maintaining the utmost accuracy in the deposition of these layers and subsequent formation of conductive and nonconductive features is critical in achieving smaller and smaller device dimensions and higher packing densities using conventional lithographic processes.
In general, lithography refers to processes for pattern transfer between various media. It is a technique used for integrated circuit fabrication in which a silicon slice, the wafer, is coated uniformly with a radiation-sensitive film, the resist, and an exposing source (such as optical light, X-rays, or an electron beam) illuminates selected areas of the surface through an intervening master template, the photoresist mask, for a particular pattern. The lithographic coating is generally a radiation-sensitized coating suitable for receiving a projected image of the subject pattern. Once the image is projected, it is indelibly formed in the coating. The projected image may be either a negative or a positive of the subject pattern. Exposure of the coating through the photoresist mask causes a chemical transformation in the exposed areas of the coating thereby making the image area either more or less soluble (depending on the coating) in a particular solvent developer. The more soluble areas are removed in the developing process to leave the pattern image in the coating as less soluble polymer.
Deposition of the photoresist mask, as well as deposition of any other layer critical to the performance of the semiconductor device, requires several parameters to be set and/or calibrated before a particular deposition or etch process may begin. However, due to wafer-to-wafer variations, the large number of factors (parameters) involved in a lithographic process, and the variability of process conditions which may arise in the chamber, pre-set process parameters may not produce consistent layers and structures.
Conventional methods typically employed to remedy these inconsistencies among wafers have proven to be both problematic and costly. Such methods usually require stopping the process to examine the wafer and then resuming the process if further processing is necessary. In some cases, the wafer may be damaged and require repair. If the damage is beyond repair, then the wafer must be discarded. In the former situation, it is difficult to obtain consistent wafers since the process and its parameters are continuously stopped and then resumed at a later time. In both situations, production costs increase, production efficiency decreases and actual product is less than effective or less than projected based on the number of wafers put into production.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention provides a system and method for obtaining consistently formed semiconductor devices. More specifically, the present invention provides a system and method for controlling the progression of a lithographic process such as a deposition or etch process. This is accomplished in part by employing one or more piezoelectric sensors, such as quartz crystal sensors, integrated into a wafer. The sensors capture and/or indicate changes in the wafer. The data received from the sensors may relate to deposition and/or etch rates, density and/or thickness, and uniformity of the subject wafer. This information may be continuously fed back into the lithographic process in order to determine the endpoint for the process. When more than one sensor is employed in this manner, data from each sensor may be cross-referenced which facilitates determining uniformity of the layer (e.g., uniform vias, trenches, layer, gates, and the like).
One aspect of the present invention relates to a feedback-driven, closed-loop system for controlling the progression of a lithography process. The system contains a wafer comprising one or more piezoelectric sensors, a voltage source and a transmitter integrated within the wafer, wherein each piezoelectric sensor is operable to generate data relating to the lithography process; an analyzer operably connected to the wafer for receiving data communicated from the transmitter; and a lithography process controller for regulating one more process parameters and one or more process components based on the data in order to facilitate consistently formed semiconductor devices.
Another aspect of the present invention relates to a feedback-driven, closed loop method for controlling the progression of a lithography process. The method includes providing a wafer comprising one or more quartz crystal sensors, a voltage source and a transmitter integrated within the wafer, wherein each quartz crystal sensor is operable to generate data relating to the lithography process; subjecting the wafer to the lithography process; and during the lithography process, measuring a frequency of the one or more quartz crystal sensor, communicating the measured frequency to an analyzer, relaying information related to the measured frequency back to a lithography process controller, and modulating a lithography process controller in-situ according to the measured frequency in order to obtain consistently formed semiconductor devices.
Yet another aspect of the present invention relates to a feedback-driven, closed loop method for controlling the progression of a lithography process. The method includes providing a wafer comprising at least two quartz crystal sensors, a voltage source and a transmitter integrated within the wafer, wherein each quartz crystal sensor is operable to generate data relating to the lithography process; applying a fixed voltage to the at least two quartz crystal sensors; subjecting the wafer to the lithography process; during the lithography process, obtaining separate data from each of the at least two quartz crystal sensors, communicating the separate data to an analyzer, feeding information corresponding to the separate data back to a lithography process controller, and modulating one or more process parameters and one or more process components in-situ according to the data in order to obtain consistently formed semiconductor devices; and cross-referencing the separate data in order to determine whether uniformity exists in at least two locations on the wafer.
Still another aspect of the present invention relates to a feedback-driven, closed loop system for obtaining consistently formed semiconductor devices. The system includes a plurality of wafers, each wafer containing one or more quartz crystal sensors, a voltage source and a transmitter integrated within the wafer, wherein each quartz crystal sensor is operable to generate data relating to the lithography process; an analyzer operably connected to each wafer for receiving data communicated from the transmitter; a processor for cross-referencing the data obtained from the plurality of wafers to determine structure uniformity among the plurality of wafers; and a lithography process controller for regulating one more process parameters and one or more process components based on the data in order to facilitate consistently formed semiconductor devices.